Distinctive terrestrial fauna (vertebrate and invertebrate) associated with supratidal plains vulnerable to sea level rise in Northern Australia

Supratidal plains support grasslands, saltmarsh and wetlands of varying salinity and hydrological regime, making them challenging environments for fauna. While known to be important habitat for birds, other faunal values are poorly understood. To assess this, we sampled a relatively undisturbed supratidal plain in a national park and compared their faunal assemblages to the bordering terrestrial habitat (3 sites/habitat). Surveys were undertaken in the post-wet and dry seasons using standard techniques for vertebrates (drift fences, pitfalls, snake traps, small mammal traps, active searching, spotlighting, bird transects, traces and ultrasonic bat detectors). Invertebrates were sampled with sweep nets. Effect of habitat and season were assessed by ANOVA on richness and abundance, and ANOSIM on assemblages. 154 vertebrate species comprising 26 herptile, 14 mammal, 11 bat and 103 birds, were found, of which 94 occurred on the supratidal plain including several endangered bird species not found in terrestrial habitats. Although lower in diversity of some groups, supratidal plains supported greater numbers and more species of shorebirds and grass-associated birds, and more species of microbats. Several mammal species, including planigales, were relatively abundant on the plain. Faunal assemblages of all groups were distinct compared with adjacent terrestrial habitats. Supratidal sites were distinguished by greater abundance of Heteroptera and wasps than the other habitats, and post-wet peaks in abundance of invertebrate taxa providing important food for breeding Capricorn Yellow Chats. These findings highlight the distinctiveness of the supratidal plain fauna and that further research is needed before plains are lost to accelerating sea level rise.